It takes a minute to sink in that Sex and the City, the debut book from Candace Bushnell that spawned the HBO hit series and two movies, was published in 1996 — nearly a quarter-century ago. Based on a series of columns she wrote for the New York Observer, the book was a frothy, decadent take on being a young single woman in New York City.

Bushnell has written seven books since then, all fiction. Now she’s returned to where it all began — and a dating landscape that has changed dramatically — with Is There Still Sex in the City?

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This time around, she is wary and bruised. By the time you reach middle age, she writes, "some real stuff has happened to you." In Bushnell's case, divorce from a ballet dancer she married in 2002 and the death of her mother. Vowing to be "man-free," she flees urban life to her second home in the country.

But as she approaches 60, she misses the pulsing excitement — and men — of New York City. It’s hard not to hear Sarah Jessica Parker’s voice-over in Bushnell’s early opener:

"And so, four years after I'd left, I returned to my old stomping grounds. As I crossed the bridge into Manhattan, now a middle-aged, single white woman driving a sensible SUV with two large standard poodles in the back, I had to ask the obvious question. Is there still sex in the city?"

Bushnell's voice is as knowing and sharp as ever. When she attends a tech billionaire's birthday party, she notes the presence of a pastry and ice cream chef. "That's the thing about rich people," she writes. "They can have anything they want but like everyone else, they all just want ice cream."

As with SATC’s “toxic bachelors” and “modelizers,” there’s a new taxonomy: “Cubbing,” the pursuit of older women by younger men; or “MAM,” for middle-aged madness, a late-onset midlife crisis for women. She also updates a chapter on “bicycle boys” — then, the charmingly rumpled literary types on vintage bikes, now wealthy guys in Lycra.

Because so much of contemporary dating begins online, Bushnell secures a magazine assignment to document her first foray onto Tinder. For research, Bushnell assembles a group of "Tinderellas" in their 20s and early 30s to fill her in. Their feedback is grim. All the guys on Tinder, one tells her, take prescription drugs. "They're like: 'The reason I can't text you back is because of ADD.'"

Dates, they scoff. What are those? One woman describes a typical outing, in which a man messaged her to meet him at a restaurant at 8 p.m. "It turned out he only wanted to meet at the restaurant to pee, and then we went to a Starbucks where we didn't even get a coffee,'" she says. "And then we got kicked out."

But Bushnell gamely goes on a Tinder date with 31-year-old Jude, the first person she’s ever met online (online dating was in its infancy when Sex and the City was published). It’s pleasant enough, but the next time around he stands her up after a drug overdose lands him in the hospital. She endures a disastrous date with a 75-year-old who, when not trying to get her into the sack, says he’s looking for “companionship.”

“Of all the micro- and macro-aggressions of aging,” Bushnell writes, “the worst one is when you discover you’ve crossed the bridge from wanting a relationship, with all that entails, to having to settle for its lesser cousin: companionship.”

As usual, female bonds are a godsend, but also the book’s weakness, as Bushnell toggles fitfully between her own story and those of many friends, and even friends of friends — most of whom are so lightly sketched that it’s hard to care about them.

Nor is it easy to relate to some of their problems. One friend, Mia, received $30 million after her hedge-fund husband divorced her. She has a brief affair with a young guy (sorry, “cub”) who maintains her air-conditioning unit, and he attempts to blackmail her. Another friend marries a rich guy who turns out to be a jerk — he threw a friend’s skis off the gondola because she asked him to put out his cigar.

But this Sex book is more ruminative than the original; winding through the amusing anecdotes is a vivid current of fear. At one point, Bushnell, who is child-free, wonders who will take care of her eventual funeral expenses. At another, as she is walking in the city, “that middle-aged drumbeat of terror — it’s all downhill from here! — was pulsing in my head,” she writes. “I was convinced that nothing good would ever happen again, that age was about to take away all of life’s excitements and pleasures.”

This dread of irrelevance is worth exploring in greater depth. Instead, she backs away and pivots to a story — a plodding 17-page story —about being hoodwinked into buying $4,000 face cream. It’s a missed opportunity, one of several in the book.

The original SATC, and its TV spin-off, has been (rightly) reappraised for its lack of diversity, its privilege, and materialism. But it did rewrite the playbook for young women by celebrating their sexual autonomy and focusing on female friendship.

Is There Still Sex in the City? is already being developed for a television series by Paramount TV. If we see female characters in midlife with robust dating and sexual lives, Bushnell may transform the culture once again. If the actresses who play them are actually in midlife, even better.

Jancee Dunn’s most recent book is “How Not to Hate Your Husband After Kids.”